120 NERVOUS TISSUE. 



and any metallic chlorides or phosphates which may be present, 

 are simultaneously decomposed ; hence it is absolutely necessary 

 to triturate the dried cerebral mass before its incineration with a 

 little carbonate of baryta a precaution which will prevent any 

 kind of loss. 



The most rational method of separating the organic, and espe- 

 cially the morphological elements, and the one which accords most 

 closely with the micro-chemical reactions, is to treat the triturated 

 cerebral mass with a dilute solution of carbonate of potash, as this 

 solution does not attack the axis-cylinder or the nerve-sheath, and 

 alters the nerve-pulp less than any other reagents, inasmuch as it 

 simply dissolves the albuminous substance and the greater part of 

 the medullary fat ; the filtered fluid certainly passes in a turbid 

 state through the filter, just as when pure water is used in place of 

 the above reagent, but here a much smaller quantity of fat is held 

 in suspension, and a much larger amount actually dissolved. Mere 

 traces only of histological elements, and often not even these, pene- 

 trate through the filter, and after repeated rinsings with the solution 

 of carbonate of potash there remains on the filter only a very little 

 fat (principally a little cerebric acid) with the other organic matters. 

 The albuminous substance of the nerve-pulp may easily be de- 

 tected in the solution by means of the ordinary reagents after the 

 fluid has been saturated with acetic acid, the precipitate separated 

 by filtration, and the suspended fat removed by ether. 



The residue of the cerebral mass, which is insoluble in car- 

 bonate of potash, and, besides a part of the cerebric acid, con- 

 tains only the axis-cylinders and the nerve-sheaths, must be heated 

 in a dilute solution of potash or soda for the purpose of dissolving 

 the acid ; from this solution the albuminous substance of the axis- 

 cylinders, together with a little cerebric acid, is precipitated by 

 acids, with the development of a little sulphuretted hydrogen. 



The residue of the cerebral matter, which is insoluble in dilute 

 solutions of the caustic alkalies and their carbonates, contains 

 scarcely anything but the nerve-sheaths and a little cerebrate of 

 lime, the latter of which may be removed by boiling this residue 

 first with dilute acetic acid, and subsequently with ether. We 

 cannot, however, unfortunately consider this residue as a chemi- 

 cally pure substratum of the nerve- sheaths, as the walls of the 

 capillaries are intermixed with it. 



The methods of investigation which we have described do not, 

 however, as we stated, suffice to separate the cerebral fats in any 

 rational manner from one another; nor can we hope to see good 



